Top end Rebuild time -'98 600

10752 Views 23 Replies 4 Participants Last post by KArthur, Mar 28, 2017

KArthur

Discussion Starter · Feb 20, 2017

2

I have been rebuilding a 1998 Grizzly 600 that I got back in October '16. It smokes quite a bit when its cold but then stops after it gets warmed up. Rode it quite a bit this past Saturday and I had to put oil in it a few times. I checked the compression with a compression tester and it is low. I have been running "Marvel mystry Oil" in the gas and oil.... thought it might free up a stuck ring... no luck. :frown2:

I think its probably time to put rings in it. I think I will go back with Yamaha rings. Notice they have over sized rings listed for these. I wont really know what I will need until I get it torn apart. What about after market gasket sets? I found Tusk and HySpeed brands for $20-$25. Looks like either kit will have all the gaskets I need, plus the valve stem guide seals. I like the HySpeed kit better just because it has more o-rings in it.

Suggestions? Any bad experiences with either of these kits?

Thanks

Kirk

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KArthur

Discussion Starter · #2 · Feb 20, 2017

Just found where Keith20mm suggested to use the Winderosa Kit. Looked them up and for my 98-600 it is Winderosa part number 810833.

Found these on Amazon for about $30.

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NewGrizz

· #3 · Feb 21, 2017

How many miles on it? Maybe also get the head rebuilt (new valve guides).

KArthur

Discussion Starter · #4 · Feb 23, 2017 (Edited)

Not sure about the mileage, but it is a bunch. It was in pretty bad shape when I got it.

Pulled the head and cylinder off last night. Checked the valves by pouring carb cleaner on top. It leaks past all four of the valves.

On the piston, there is a 1.0 stamped on the top. I assume this means it is 1.0mm oversized already, so someone has done this before. I suspected the head had been off because they put the springs on upside down. My piston skirt measures Ø3.778 (95.94mm)

Bad news is the piston bore measures Ø3.790 (96.266mm), which is already out of spec for 1.0mm oversize. From the service manual, it shows the wear limit to be 95.1mm, so I think the wear limit for 1.0 over would be 96.1mm, or Ø3.783. I am .007 over this already.

I don't see any rings larger than 1.0 over from Yamaha. Does anyone know if I can get a 2.0 over piston ring set? Time for a new piston/jug?

I did see a Wisco 97mm (+2.0mm) on ebay for $120. Alternatives?

Thanks

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dezz

· #5 · Feb 23, 2017

Yamaha never offers a larger overbore than 1mm. This is for reliability reasons. Past that limit and ultimate reliability can be compromised, especially heat.

To go bigger you will need aftermarket. That Wiseco piston kit should be fine. Due to the 600's reputation for running hot (and they do), I recommend mounting the oil cooler to the front rack. Possibly installing a larger automotive cooler. This will help with heat the overbore piston is going to make.

NewGrizz

· #6 · Feb 24, 2017

I would pass on the forged piston. The piston clearance is wider for forged Pistons which allows for more piston expansion and makes for a noisy piston/cylinder slap until it warms up. The 600 is already a noisy beast and you will think it is coming apart when you start it up. And you will already be at the limits of boring again. I would sleeve it back to stock. Contact NFLOW. I think They are site sponsors here. They did my crank and cylinder work for my 600 last summer.

KArthur

Discussion Starter · #7 · Feb 25, 2017

Whats wrong with this picture? :grin2:

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KArthur

Discussion Starter · #8 · Feb 25, 2017

NewGrizz said:
I would pass on the forged piston. The piston clearance is wider for forged Pistons which allows for more piston expansion and makes for a noisy piston/cylinder slap until it warms up. The 600 is already a noisy beast and you will think it is coming apart when you start it up. And you will already be at the limits of boring again. I would sleeve it back to stock. Contact NFLOW. I think They are site sponsors here. They did my crank and cylinder work for my 600 last summer.

I sent NFLOW a email to see what they would charge me to do that.

As far as clearance, what clearance should there be for a forged piston? Right now, I have .012 in. I thought that was excessive, but it may not be if I have a forged piston. My bike is/was pretty noisy. I thought it was the wrist pin, but it is not out of spec. Is this a forged piston or can you tell from this?

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NewGrizz

· #9 · Feb 25, 2017

KArthur said:
Whats wrong with this picture? :grin2:

Right valve spring is upside down. The tighter coils (more mass) should be on the bottom and less mass at the top of the valve where the spring has the most movement (up and down). That's my $0.02 worth.

NewGrizz

· #10 · Feb 25, 2017

KArthur said:
I sent NFLOW a email to see what they would charge me to do that.

As far as clearance, what clearance should there be for a forged piston? Right now, I have .012 in. I thought that was excessive, but it may not be if I have a forged piston. My bike is/was pretty noisy. I thought it was the wrist pin, but it is not out of spec. Is this a forged piston or can you tell from this?

Can't tell. Most likely its cast (cheaper) but that's a guess. Look underneath at the wrist pin area and see if there is a manufacturer name or mark/logo.

NewGrizz

· #11 · Feb 25, 2017

Check for end play (vertical) at the connecting rod on the crankshaft. You don't want to be in it this far and not check that.

KArthur

Discussion Starter · #12 · Feb 25, 2017

NewGrizz said:
Right valve spring is upside down. The tighter coils (more mass) should be on the bottom and less mass at the top of the valve where the spring has the most movement (up and down). That's my $0.02 worth.

Your right. That's how it was when I took the cover off. Everything I touch on this bike, I find something put together wrong. Will it make any difference in the way it runs? Probably not much, but that's not how it's designed to be. It just shows me that whoever done this either didn't know what they were doing or got lucky on three out of four.

KArthur

Discussion Starter · #13 · Feb 25, 2017

3

I looked on the back side of piston and its a Yamaha.

Progress today... got the valves out and lapped them in. They seal MUCH better now. Amazing how much build-up was on them. I also installed a kit in the carburetor. I talked to a local machine shop and they can do the bore if thats the direction I take. I am kind of leaning going with an oversized piston unless the cost to sleeve it is very reasonable.

Before

After

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NewGrizz

· #14 · Feb 26, 2017

My 600 had the same issue smokin like a train and the same size piston as yours (Yamaha) with double the piston/cylinder clearance when I bought it.

NewGrizz

· #15 · Feb 26, 2017

Did you check for end play on the connecting rod at the crank shaft yet??

KArthur

Discussion Starter · #16 · Feb 26, 2017

NewGrizz said:
Did you check for end play on the connecting rod at the crank shaft yet??

Just did.... 0.020in. That is side to side (horizontal). I didnt see that spec in the SM. What should it be?

There is no play vertically.

KArthur

Discussion Starter · #17 · Mar 3, 2017

I ordered a Ø97mm (+2mm) piston from Wiseco. Got it in yesterday and carried it with the jug to my machine shop. They are going to bore it .0025 over the piston diameter.

Should have it back Monday and I can get going the other way with it.

KArthur

Discussion Starter · #18 · Mar 13, 2017

Just to follow up. Everything went good on the rebuilding the top end. On the valves, I did not have them ground. Instead I hand lapped them. Before I did it they would not hold a good vacuum. All of them would leak.... but afterwards they held a good vacuum, so I called that good and moved on. Of sourse, I replaced the valve stem seals which were in the Hyspeed Set (see first post).

All of the gaskets in the Hyspeed set fit well. I had a couple o-rings left over that I did not know where they went. It would be good if they had a diagram of where they go. Its pretty obvious on the gaskets, but not on all of the o-rings.

I used the 97mm (which is +2mm over factory) Wisco piston and rings. The machine shop made the bore +.0025in over my piston size. I had to grind a small amount off each ring to get the end gap on them correct. That was to be expected I guess.

No more smoking now! Engine is MUCH quieter. I don't hear all the ticking and rattling when I rev it up. I could not be happier about the way it runs now.:grin2:

Quick run down of all that I did. Its alot of work. Total price tag....$305 + Labor.
Bored cylinder ($90)
New Wisco piston and rings ($120)
New Yamaha timing chain ($40)
Hand lapped valves seats ($5)
New valve stem seals (HySpeed Seal Kit $30).
Set intake and exhaust valve clearance per service manual.
Rebuilt carb with kit that I got off ebay from "SledPartsGuy" ($20)

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daniel.s.white.op

· #19 · Mar 14, 2017

First time poster. Usually read but found it amusing as I just put that same kit in my 98. And finished it this morning. Have a friend that rebuilds big blocks do the machining for me. Super happy with all of it too. It makes me happy to think people rebuild theses rather than throw them out.

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daniel.s.white.op

· #20 · Mar 14, 2017

Wanted to add I agree and did, throw a bigger cooler and fan in the front.

Northern Maine... 10 weeks till trails

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